EP0211965B1 - Liquid-container of thermoplastic material, especially fuel, and its production method and shape - Google Patents

Abstract

1. A method of manufacturing a storage tank (B), made of thermoplastic material, for liquids, in particular fuel oil, wherein at least two constituent tanks (E1 , E2 ) are moulded simultaneously in a blow mould (F1 , F2 ) or a rotational mould and can be connected to one another at least by a lower and an upper connecting passage (1, 2), wherein the constituent tanks (E1 , E2 ) and the connecting passages (1, 2) may at the same time be moulded as one piece, characterised in that the substantially cuboid constituent tanks (E1 , E2 ) are moulded in a position relative to one another in which the constituent tanks (E1 , E2 ) are only close together at one edge or in the vicinity of one edge and the connecting passages (1, 2) are formed on these edges, and, following removal of the part from the hollow mould (F1 , F2 ), in order to bring the constituent tanks (E1 , E2 ) into the final form, they are pivoted together about said tank edges or about a bending axis in the vicinity thereof, wherein the connecting passages (1, 2) are deformed and the constituent tanks (E1 , E2 ) approach one another, preferably into a relative position in which the side walls (3, 4) of the cube are parallel to one another.

Description

The invention relates to a method for producing a storage container for liquids, in particular heating oil, made of thermoplastic, whereby at least two elementary containers are molded simultaneously in a blow mold or a rotary mold and the elementary containers are connected to one another by at least one lower and one upper connecting channel, wherein the elementary containers and the connecting channels are simultaneously formed as an integral part.

Plastic storage tanks for heating oil or any other liquid goods are manufactured with different capacities. Usually, several containers are put together to form a container battery, also known as a battery tank. In general, the larger the capacity of a container, the greater the wall thickness of the container must be. It is known to limit the wall thickness of containers with large capacity by dissolving the entire container in elementary containers. The elementary containers can have much smaller wall thicknesses than containers with large walls. For safety reasons, it is mandatory that the connecting channels between the elementary containers consist of them in one piece. It is therefore not permissible to flange the lower connecting channels, in particular, via which neighboring elementary containers communicate with one another, to the elementary containers.

In a known container (DE-PS 2 758 838), the elementary containers are cylindrical, arranged in a row and connected to one another via connecting channels. The connecting channels lie in a longitudinal median plane of the container. Distances are provided between the elementary containers, which cannot be avoided because of the design of the hollow form in which the container is formed. There are also unused space gussets between the cylindrical elementary containers, so that the actual capacity is substantially smaller than a cuboid space comprising the container and describing the space requirement of the container.

The invention is based on the object of proposing a method of the type mentioned at the outset with which storage containers can be produced which, in relation to their space requirement, have a considerably larger capacity than the known storage containers which are dissolved in elementary containers. The invention is also intended to propose design features for the container that are particularly advantageous for the basic concept. Finally, a shape for the production of the container is also to be proposed by the invention.

This object is achieved with the features of claims 1, 7 and 20, respectively.

The invention ensures that the elementary containers can be moved close together, preferably wall to wall, so that no unused space remains between the elementary containers. Further contributes to the better utilization of the space that the elementary containers are cuboid, so that there are no gussets between the elementary containers. The arrangement of the connecting channels on edges instead of in the longitudinal center plane, as is the case with the known container according to DE-PS 2 758 838, is also an essential feature which contributes to the elementary containers being able to be joined together with or without a gap.

When using the blow molding process, it is advantageous to pivot the containers immediately after removal from the mold, since at this stage the connecting channels are still flexible (claim 2). A good flexibility of the connecting channels can be achieved in particular with a special temperature control according to claim 3.

The invention is applicable not only for the production of containers in the blow molding process, but also for the production of containers in the rotary process. The necessary plasticity can also be produced according to claim 4 by heating the connecting channels. Such subsequent heating is of course also possible with blown containers.

As already mentioned above, it is preferable that the elementary containers are placed against one another without a space. However, small gaps may be appropriate, e.g. to allow an inspection of the elementary containers from the outside.

The method according to the invention is also particularly suitable for using the same shape to produce both independent elementary containers and larger containers which consist of two or more elementary containers, connection channels not being produced in the former case, while connection channels are formed in the case of larger containers. In the case of blown containers, the plastic plastic tube extruded into the mold is then squeezed in the space between two elementary containers. This enables a very efficient production of containers with single, double, triple, etc. capacity. For example, an elementary container can have a capacity of 1000 liters, so that containers with e.g. 1000 liters, 2000 liters and 3000 liters capacity can be produced.

Regarding the term "cuboid" it should be noted that "essentially cuboid" should also be understood to mean containers which are strongly rounded at their edges, in particular at their vertical longitudinal edges, in order to maintain a high overall strength of the container at a given wall thickness. The elementary containers can also have circumferential constrictions which further improve the strength. "Substantially cuboid" is thus intended to mean that a geometric cuboid is filled as completely as possible, taking into account the design features necessary for good strength, deviations in the volume of an elementary container from the volume of a circumscribing purely geome cubic cubic in the range of 5% to 15% of the volume of the geometric cuboid should be allowed and fall within the scope of the invention. If the elementary container is discussed in connection with the invention of edges, in particular side edges, it is generally not a question of edges in the narrower sense, but of the vertical corner regions of the elementary containers, which, as said, are rounded off with large radii can be and are then, for example, parts of cylindrical surfaces.

The cavities of the mold are preferably divided diagonally. With this type of division, the blow molding process extrudes the tube of plastic plastic material extruded between the mold halves as evenly as possible, thereby achieving a wall thickness that is as uniform as possible. This contributes to the saving of plastic material.

The inclination of the cuboid cavities to one another has the advantage that, after demolding, relatively small swiveling movements of the elementary containers are sufficient to bring them into the end position relative to one another. However, the cavities can also be arranged relative to one another, which has the advantage that both halves of the shape are the same, as a result of which the shape can be produced cheaply.

Interchangeable insert parts can be quickly replaced with little effort, so that independent elementary containers or larger containers can be produced, which consist of several elementary containers, as required. So far, the transition to a different container size has involved extensive assembly work (removing a large and heavy mold and inserting a new, heavy mold, e.g. into a blow molding machine), which meant that a molding machine had to be down for a long time. The possibility of being able to produce different container sizes with the same mold is also a very important investment advantage, since such large molds are very expensive. Insert parts for a blow mold advantageously have a cavity for receiving displaced plastic material.

A special cuboid shape is advantageously provided for the elementary containers, namely the shape of a square column. Containers shaped in this way are particularly advantageous in terms of strength, since all side walls have the same dimensions and the approximation to a cylindrical shape, which would be optimal in terms of strength, is particularly good.

The connecting channels can be shaped differently. They can have a flat, upright cross section. In this case, it is advantageous to support the large walls against one another by cusps molded onto them. The connection channels can also have a circular cross section, in which case support bumps are not required. The connecting channels preferably have corrugated walls, which facilitates the flexibility of the connecting channels.

Adjacent elementary containers are preferably locked together. Various embodiments are specified in the claims for the formation of the lock.

According to a further embodiment of the invention, the elementary containers engage in one another in a form-fitting manner, elevations on one elementary container engaging in recesses on the other elementary container.

In the case of a container which is composed of a plurality of elementary containers, the necessary nozzles are advantageously arranged on the ceiling of the elementary container concerned only on one elementary container. This is sufficient, since all elementary containers communicate with each other. On the other hand, it is advantageous to provide the possibility of attaching sockets to each elementary container, which is necessary if each elementary container is to be an independently usable container.

• Fig. 1 eine Draufsicht auf zwei Elementarbehälter im Stadium unmittelbar nach der Entnahme aus einer Form,
• Fig. 2 eine Draufsicht auf einen fertigen, aus zwei Elementarbehältern bestehenden Behälter, wobei die beiden Behälter nach Fig. 1 durch Schwenken aneinandergefügt sind,
• Fig. 3 eine Seitenansicht des Behälters in Richtung des Pfeiles 111 in Fig. 2,
• Fig. 4 einen Querschnitt durch eine Blasform mit abgeknickter Teilungsebene,
• Fig. 5 einen Querschnitt durch eine Blasform mit durchlaufender Teilungsebene und gleich ausgebildeten Formhälften,
• Fig. 6 einen vertikalen Schnitt durch einen Verbindungskanal entsprechend der Linie VI-VI in Fig. 3 in einem gegenüber Fig. 3 vergrößerten Maßstab,
• Fig. 7 einen Längsschnitt durch einen Verbindungskanal entsprechend der Linie VII-VII in Fig. 6,
• Fig. 8 einen Querschnitt durch einen Verbindungskanal mit kreisrundem Querschnitt,
• Fig. 9 einen Längsschnitt durch den Kanal nach Fig. 8 entsprechend der Linie IX-IX in Fig. 8,
• Fig. 10 eine Verriegelungsstelle zwischen zwei Elementarbehältern in Seitenansicht entsprechend dem Pfeil X in Fig. 11,
• Fig. 11 eine Draufsicht auf die Verriegelungsstelle entsprechend dem Pfeil XI in Fig. 10,
• Fig. 12 eine Ansicht einer Verriegelungsstelle gemäß einer weiteren Ausführungsform der Erfindung in Richtung des Pfeiles XII in Fig. 13,
• Fig. 13 eine Draufsicht auf die Verriegelungsstelle entsprechend dem Pfeil XIII in Fig. 12,
• Fig. 14 eine Seitenansicht eines Lagerbehälters, dessen Elementarbehälter durch Zuggurte miteinander verbunden sind,
• Fig. 15 einen horizontalen Teilschnitt nach Linie XV-XV in Fig. 14 in einem gegenüber Fig. 14 vergrößerten Maßstab, wobei nur die äußeren Eckbereiche der Elementarbehälter dargestellt sind und
• Fig. 16 einen Batterietank, bestehend aus drei Lagerbehältern, von denen jeder aus zwei Elementarbehältern besteht.

Exemplary embodiments of the invention are shown in the drawing. Show it:

• 1 is a plan view of two elementary containers in the stage immediately after removal from a mold,
• 2 shows a plan view of a finished container consisting of two elementary containers, the two containers according to FIG. 1 being joined together by pivoting,
• 3 shows a side view of the container in the direction of arrow 111 in FIG. 2,
• 4 shows a cross section through a blow mold with a bent parting plane,
• 5 shows a cross section through a blow mold with a continuous parting plane and identical mold halves,
• 6 shows a vertical section through a connecting channel along the line VI-VI in FIG. 3 on an enlarged scale compared to FIG. 3,
• 7 shows a longitudinal section through a connecting channel along the line VII-VII in FIG. 6,
• 8 shows a cross section through a connecting channel with a circular cross section,
• 9 is a longitudinal section through the channel of FIG. 8 along the line IX-IX in FIG. 8,
• 10 shows a locking point between two elementary containers in a side view corresponding to the arrow X in FIG. 11,
• 11 is a plan view of the locking point according to the arrow XI in Fig. 10,
• 12 is a view of a locking point according to a further embodiment of the invention in the direction of arrow XII in FIG. 13,
• 13 is a plan view of the locking point according to the arrow XIII in Fig. 12,
• 14 shows a side view of a storage container, the elementary containers of which are connected to one another by tension belts,
• 15 shows a horizontal partial section along line XV-XV in FIG. 14 on an enlarged scale compared to FIG. 14, only the outer corner regions of the elementary containers being shown and
• Fig. 16 is a battery tank consisting of three La containers, each consisting of two elementary containers.

The storage container B according to FIGS. 2 and 3 consists of two elementary containers E _i , E2, which communicate with one another via a lower connecting channel 1 and an upper connecting channel 2. The elementary containers Ei, E2 and the connecting channels 1, 2 consist of a coherent piece.

In the form still to be described, the elementary containers E _i , E2 have a relative position to one another, as is shown in FIG. 1. Here, the side walls 3, 4, which lie against one another later, run at an angle a to one another, which in the example shown is 45 _° . On the side wall 3 there is a depression 5 and on the side wall 4 there is an elevation 6 which engages in the depression after pivoting together (state according to FIG. 2). After swiveling together, the two elementary containers are fixed to one another in their swiveled-together position by locking points 7. Two height-offset locking points 7 are preferably provided, which can be approximately at the height of the connecting channels 1, 2, for example.

The elementary containers are essentially in the form of a square column. However, where a square pillar has its longitudinal edges, there are roundings 8 which have a relatively large radius. In the lower third of each elementary container there is also a circumferential constriction 9; in the middle of the height of the constriction 9, each elementary container has a circular cross section. A ceiling 10 of each elementary container in turn merges with roundings 11 with a large radius in the container side walls. The container bottom 12 of each elementary container merges with edges 13 into the container side walls. The shape described is essentially only the shape of a strictly geometric square column. The deviations described arise from the need to optimize the shape in terms of strength.

There are three nozzles on the elementary container E2, namely a ventilation nozzle 14, a removal nozzle 15 and a filling nozzle 16. No nozzles are provided on the ceiling 10 'of the elementary container E ₁ .

The storage container B can be produced both in a blow mold and in a rotary mold. In the following it is assumed that the container was produced by the blow molding process. Blow molds are shown in cross-section in FIGS. 4 and 5.

4 has two essentially cuboid cavities H ₁ and H ₂ . The shape designated overall by Fi consists of two mold halves 17, 18 which can be joined together on a separating surface 19. The separating surface 19 runs essentially diagonally over the cavities Hi, H ₂ and is bent over the edge 52, which roughly corresponds to the later bending line of the connecting channels 1, 2. This bend results from the fact that the cavities Hi, H ₂ are to each other such that the angle β between the walls 20, 21 of the mold cavities Hi, H ₂ is less than 90 °, in the present case, this angle is 45 _°.

In the area in which the mold cavities Hi, H ₂ come closest, the mold contains insert pieces 22, 23. The insert pieces have such a shape that there are 1, 2 mold connection channels 24 in the area of the connecting channels to be produced.

When a container is being produced, the mold halves 17, 18 are first moved far apart in the direction of the arrows 25, 26. Between the two mold halves, a hose is extruded in a blow molding machine, in which the mold F _{i is} installed, and is still in a good plastic state initially hangs between the mold halves 17, 18. When the hose is completely extruded, the mold halves are moved together. After the mold has been closed, the space inside the tube is inflated, the tube wall being pressed against the inner walls of the cuboid cavities H ₁ , H ₂ . Here, the connecting channels 1, 2 also form.

After a certain cooling time (cooling channels for cooling water (not shown in the drawing run in the walls of the mold) the mold is opened. The elementary containers are already sufficiently stable at this stage to be able to be handled. On the other hand, the connection channels 1, 2 can still be shaped, which can also be brought about in a targeted manner in that the shape in the area of the shape connection channels 24 is cooled less than in the rest of the area. The elementary containers E ₁ , E2 formed in the mold cavities Hi, H ₂ are now brought into the relative position according to FIG. 2 to one another, as has already been described. The necessary deformation of the connecting channels is relatively small because of the relatively small angle β, which is advantageous for the production.

The mold F ₂ in FIG. 5 has mold halves 27, 28 which are of identical design. The mold halves can be separated and joined together on a continuous separating surface 29. The mold halves include cavities H ' ₁ and H' ₂ , which are oriented somewhat differently relative to one another than the cavities Hi, H _{2 of} the mold F ₁ . The angle β 'between the cavities is 90 _° here. This arrangement has the advantage that the mold halves 27, 28 can be made the same. However, the connecting channels between the elementary containers then have to be deformed more than when manufactured in the form Fi.

The form F ₂ contains inserts 30, 31 which separate the cavities H ' ₁ and H' ₂ from each other. The mold F ₂ could also contain moldings that leave mold connection channels between the cavities H ' ₁ and H' ₂ open. Connectors 30, 31, which separate the cavities, are used when elementary containers are to be produced that can be used independently. In this case, of course, the necessary connectors must be molded onto both elementary containers.

The inserts 30, 31 and 22, 23 are quickly replaceable, as are the inserts for forming additional nozzles, so that a shape of manufacture is large with only minor conversion work ßer containers, which consist of several elementary containers, can be converted to the production of the smallest units, in which independent elementary containers are produced.

The inserts 30, 31 enclose a cavity 32 which is intended to hold plastic material which is obtained when the hose is squeezed. The space 32 extends over the entire height of the cavities H ' ₁ and H' ₂ . Correspondingly, even when inserts are used that leave the mold connecting channels open, there are cavities outside of these inserts in the area of the separating surface 19 or 29 for the reception of plastic material displaced during the squeezing.

The nature of the connecting channels 1, 2 is shown in FIGS. 6, 7. As shown in FIG. 6, the connecting channel 1 (the connecting channel 2 is of identical design) has a flat cross section with large side walls 33, 34. The side wall 33 merges into the side wall 34 via rounded portions 33a, 33b. In order to prevent the connecting channel from being squeezed together, in particular when the connecting channels are deformed during the pivoting of the elementary containers E ₁ , E2, bumps 35, 36 are integrally formed on the side walls 33, 34. After a certain narrowing of the channel, these come into contact with one another and prevent further squeezing. The clear cross section Q is at least equal to the cross section of the filling line which is to be connected to the filling nozzle 16. This ensures that communication between the two containers is possible without throttling, which hinders the compensation of the filling levels in the elementary containers.

The wall of the connecting channel is corrugated, which is shown in Fig. 7. Bead-shaped elevations 37 running around the channel wall alternate with channel-shaped depressions 38. This shape also improves the bendability of the connecting channels. The bending axis lies approximately in the area of the inner side wall 34 of the channel 1.

8 and 9, a connecting channel 1 'is shown, which can be used instead of the channel according to FIGS. 6 and 7. This connecting channel has a circular cross section, as can be seen from FIG. 8. This channel also has a corrugated wall (see FIG. 9) with bead-shaped elevations 37 'and trough-shaped depressions 38'. A connecting channel according to FIGS. 8 and 9 is dimensionally stable, so that there is no fear of crushing even when bending. In particular, the ribbing, which is formed by the elevations 37 and the depressions 38, also contributes to increasing the rigidity.

10 and 11 show the formation of a locking point, as it is e.g. can be provided at 7 (see Fig. 2). There is an eye 39 or 40 on each of the elementary containers to be locked. The eyes are offset in height such that they can overlap one another. A connecting bolt 41 made of plastic is inserted through mutually aligned bores in the eyes. The ends 41a, 41b of the bolt are crimped like a rivet, whereby the bolt 41 is axially secured.

The eyes 39, 40 are components of welded parts 42 of the same design. be injection molded from thermoplastic. Each welding part 41 has a welding flange 43 which is connected to the container wall by welding. During the manufacture of the container, the welding parts 42 are inserted into the blow mold. When the container is blown, the weld-on parts weld to the weld-on flanges 43 with the container wall.

In the variant according to FIGS. 12 and 13, the elementary containers Ei, E2 are held together by clips 44. The clamp 44 engages around strips 45, 46, which in turn are components of weld-on parts. In the embodiment according to FIGS. 12 and 13, the welded-in parts to be connected with the clamp 44 are at the same height, while in the embodiment according to FIGS. 10 and 11, as stated, there is a height offset. As the top views of FIGS. 11 and 13 show, the connection structures lie within a plane 47 which is applied to the side wall of the container.

14, which shows a further connection construction, also shows that there are two locking points above the height of the container. The locking points described so far can be arranged at the same point as the straps 48, 49, which are used in the storage container according to FIGS. 14 and 15.

According to FIGS. 14 and 15, eyelets 50 and 51 are integrally formed on each elementary container, through which a belt 48 is pulled. Two possible connection types are shown. In the type of connection shown on the elementary container egg, the belt 48 has at its end a loop 53 which is pushed through the eyelet 50 and through which a bolt 54 is inserted. At the connection point on the elementary container E2, a loop 55 encompasses an area 56 of the tab in which the eyelet 51 is located. The two types of connection can also be used in combination. There are recesses 57 in the walls of the elementary containers Ei, E2, in which the belts lie. As a result, the straps are fixed against hanging down and do not protrude laterally over the container wall. 14 and 15 also lie entirely within a front contact plane corresponding to plane 47 in FIG. 11.

16 shows a battery tank consisting of three containers B. The elementary containers E _i , E2 lie against one another without a gap, while there are distances 58, 59 between the individual containers B. This also enables a visual inspection of the container from the side. In principle, however, it is possible to omit the gaps 58, 59 to further save space. Since neither the connecting channels nor the locking constructions protrude laterally, the containers B can be moved closer together.

The three containers B are connected to one another by a ventilation line 60, a removal line 61 and a filling line 62. The lines 60, 61, 62 are connected to the connecting pieces 14, 15 and 16, respectively.

The invention has been described using the example of a container B, which consists of two elementary containers Ei, E2. However, a container B can also consist of more than two elementary containers. Containers consisting of three elementary containers can also be used in a particularly practical manner.

Claims (26)

1. A method of manufacturing a storage tank (B), made of thermoplastic material, for liquids, in particular fuel oil, wherein at least two constituent tanks (Ei, E₂) are moulded simultaneously in a blow mould (F₁, F₂) or a rotational mould and can be connected to one another at least by a lower and an upper connecting passage (1, 2), wherein the constituent tanks (Ei, E₂) and the connecting passages (1, 2) may at the same time be moulded as one piece, characterised in that the substantially cuboid constituent tanks (E₁, E₂) are moulded in a position relative to one another in which the constituent tanks (Ei, E₂) are only close together at one edge or in the vicinity of one edge and the connecting passages (1, 2) are formed on these edges, and, following removal of the part from the hollow mould (Fi, F₂), in order to bring the constituent tanks (E₁, E₂) into the final form, they are pivoted together about said tank edges or about a bending axis in the vicinity thereof, wherein the connecting passages (1, 2) are deformed and the constituent tanks (E₁, E₂) approach one another, preferably into a relative position in which the side walls (3, 4) of the cube are parallel to one another.

2. A method as claimed in claim 1, characterised in that, following moulding of the tank (B) by the blow moulding method, the constituent tanks (Ei, E₂) are pivoted into the final form directly following removal of the tank from the mould, when the connecting passages (4, 2) are still in an almost plastic state.

3. A method as claimed in claim 2, characterised in that the connecting passages (1, 2) in the hollow mould (Fi, F₂) are kept at a higher temperature than the walls of the constituent tanks (E₁, E₂).

4. A method as claimed in claim 1, characterised in that following removal of the tank from the mould, the connecting passages are plasticized by heating and then the constituent tanks are pivoted into the final form.

5. A method as claimed in any of the above claims, characterised in that when pivoted into the final form, the side walls (3, 4) of the constituent tanks (Ei, E₂) are in abutment

6. A method as claimed in claims 1 to 5, characterised in that the constituent tanks (Ei, E₂) are moulded by blow moulding, wherein a tube, which is made of deformable plastics material and is extruded into the mould (F₁, F₂), is compressed in the intermediate space between the two constituent tanks (Ei, E₂).

7. A mould for carrying out the method in claim 1, characterised in that the mould (F₁, F₂) contains at least two substantially cuboid hollow chambers (Hi, H₂; H'₁, H'₂), the cuboid hollow chambers are adjacent to each other in the region of one of their edges, the connecting passages (1, 2) are disposed in the region of these edges and the separating faces (9, 19, 29) extend diagonally across the cuboid hollow chambers (H₁, H₂; H'₁, H'₂).

8. A mould as claimed in claim 7, characterised in that adjacent sides (20, 21) of the cuboid hollow chambers (H₁, H₂) enclose an angle (β) which is less than 90_°, preferably between 30_° and 60_°, preferably about 45_°.

9. A mould as claimed in claim 7, characterised in that adjacent sides (20, 21) of the suboid hollow cavities (H'₁, H'₂) enclose an angle (β) of 90_°, a separating plane (29) runs straight through the entire mould (F₂) and the two mould tanks (27, 28) have the same form.

10. Use of the mould of claims 7 to 9 to manufacture constituent tanks, characterised by replaceable inserts (22, 23; 30, 31), wherein inserts (22, 23) for the manufacture of tanks (B) made of connected constituent tanks (E₁, E₂) leave connecting passages (24) in the mould for moulding the connecting passages (1, 2) between the cuboid hollow chambers (H₁, H₂, H'₁, H'₂), and inserts (30, 31) for the manufacture of separate constituent tanks close off the connection between adjacent cuboid hollow chambers (Hi, H₂; H'i, H'₂) and, preferably, further replaceable inserts are provided using which tank connections or a smooth tank lid may be moulded as required.

11. Use as claimed in claim 10, characterised in that, for blow moulding, the inserts (30, 31) together enclose a hollow chamber (32) for receiving plastics material, which is displaced when the plastic tube extruded between the mould halves (27, 28) is compressed.

12. A storage tank (B) made of thermoplastic material for storing liquids, in particular fuel oil, which comprises at least two constituent tanks (E_i, E₂), which are connected to one another by way of at least one lower and one upper connecting passage (1, 2), the passages (1, 2) being formed in one piece with the constituent tanks (E₁, E₂), characterised in that the constituent tanks (E_i, E₂) are substantially cuboid and adjacent side walls (3, 4) of the constituent tanks (Ei, E₂) are parallel to one another and close to one another, possibly without any intermediate space, and connecting passages (1, 2) only extend between two adjacent edges or in the vicinity of such edges of the constituent tanks (Ei, E₂).

13. A storage tank as claimed in claim 12, characterised in that the constituent tanks (Ei, E₂) are substantially in the form of square columns.

14. A storage tank as claimed in claim 12, characterised in that the connecting passages (1, 2) have a flat cross section whose long side walls run parallel to the side walls of the constituent tanks (Ei, E₂).

15. A storage tank as claimed in claim 14, characterised in that the walls (33, 34) of the connecting passages (1, 2) are supported against each other by protuberances (35, 39) moulded onto the side walls (33, 34) of the passages.

16. A storage tank as claimed in claim 13, characterised in that the connecting passages (1') have a circular cross section.

17. A storage tank as claimed in any of claims 12 to 16, characterised in that the connecting passages (1, 2; 1') have walls which are corrugated in such a way that the connecting passages are alternately constricted and enlarged annularly.

18. A storage tank as claimed in any of claims 12 to 17, characterised in that adjacent constituent tanks (Ei, E₂) are interlocked in such a way that they are held together when the tank (B) is in its final form, for example on side edges which are opposite the side edges on which the connecting passages (1, 2), are located, wherein locking points are preferably located approximately on the level of the connecting passages (1, 2) wherein the locking means preferably lie in an imaginary plane positioned next to the side wall of the tank.

19. A storage tank as claimed in claim 18, characterised in that eyes (39, 40) are disposed on the constituent tanks (Ei, E₂) and their bores are aligned one above the other, and connecting pins (41) pass through said eyes, preferably pins made of synthetic material, whose ends (41a, 41b) are compressed in the manner of a rivet (Fig. 10, 11).

20. A storage tank as claimed in claim 18, characterised in that strips (45, 46) are disposed on the constituent tanks (Ei, E₂) and are clamped to one another by way of profiles (44) having a C-shaped cross section.

21. A storage tank as claimed in either of claims 19 and 20, characterised in that the eyes (39, 40) or strips (45, 46) are on shaped parts (42) which have a welded-on flange (43), which is welded onto the wall of the constituent tanks (Ei, E₂).

22. A storage tank as claimed in claim 18, characterised in that the constituent tanks (E₁, E₂) are connected to one another by way of tension elements (48, 49), in particular bands, which preferably lie in recesses (57) in the walls of the constituent tanks (Ei, E₂).

23. A storage tank as claimed in claim 22. characterised in that the constituent tanks (E₁, E₂) have projections (56) with openings (51) formed on them, preferably on the outer side edges, and the bands (48, 49) pass through the openings (51).

24. A storage tank as claimed in any of claims 12 to 23, characterised in that the constituent tanks (Ei, E₂) are connected to one another on their adjacent side walls (3, 4) by projections (6) and recesses (5), into which the projections (6) engage.

25. A storage tank as claimed in any of claims 12 to 24, characterised in that, in storage tanks (B) comprising a plurality of constituent tanks (Ei, E₂), connecting pieces (14, 15, 16) for a venting line (60), a bleed line (61) and a filling line (62) are provided on the lid (10) of only one of the constituent tanks (E2).

Images